DRAINAGE. 99 



which have ascertained that water, charged with matters 

 which are known to stimulate vegetation, when filtered 

 through 4 feet of retentive soil, comes out pure.* But to 

 return to our wheat. In the first case, it shrinks before 

 the cold of evaporation and the cold of water of attraction, 

 and it sickens because its feet are never dry ; it suffers the 

 usual maladies of cold and wet. In the second case, the 

 excess of cold by evaporation is withdrawn ; the cold water 

 of attraction is removed out of its way ; the warm air from 

 the surface, rushing in to supply the place of the water 

 which the drains remove, and the warm summer rains, 

 bearing down with them the temperature which they have 

 acquired from the upper soil, carry a genial heat to its 

 lowest roots. Health, vigorous growth, and early maturity 

 are the natural consequences. 



We think we have established that all soils will be bene- 

 fited by the removal of the water-table to 4 feet, which 

 must suffice under this head ; and we think every candid 

 reader will be convinced that, by this single operation of 

 lowering the water-table, many soils, hitherto sterile, and 

 consequently much underrated, may be made into useful 

 agricultural land. We will take together the fourth and 

 fifth heads : they will occupy only a few sentences. They 

 relate to the depth and direction of the drains by which 

 the water-table is to be lowered. 



Water can only get into drains by gravity, which only 

 acts by descent technically, by fall ; the fall must be pro- 

 portioned to the friction which the water encounters on its 

 passage. Suppose drains 4 feet deep to be placed 12 yards 

 apart on level land, it is plain that water at that depth, 

 lying at the intermediate point between the two drains, 

 will not get into either of them. A fall of some inches 

 will be required to enable it to overcome the friction of 

 6 yards of retentive soil. In order, therefore, to lower 

 the water-table to 4 feet at all points, the drains must be 



* Since this Essay was first printed, a portion of these experiments 

 has been communicated to the public by Professor Way. 



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